Field of the Invention
The invention relates to a method and a device for image processing of intensity images having a ring structure, in particular for processing interferograms.
The invention relates to a method and device for image processing of intensity images having a ring structure, and in particular, a method and device for processing interferograms. More particularly, the present invention relates to an image processing method and apparatus that can draw inferences relating to extremely small changes in wavelength by accurate measurement of ring radii in interferograms.
Background Information
This invention concerns itself with the same basic formulation of the problem as do the method and the device that are disclosed in DE 10 2006 030 399 B3. One of the aims is, for example, to draw inferences relating to extremely small changes in wavelength by accurate measurement of ring radii in interferograms.
Various spectroscopic measurement methods are known in which, for example, minimal changes in length or wavelength are determined quantitatively by evaluating interferograms produced by using an optical radiation. By way of example, such interferograms exhibit annularly arranged intensity extremes, for example intensity maxima and intensity minima of Fabry-Perot interference images.
DE 10 2006 030 399 B3 discloses a method and a device that enable a quick evaluation of such intensity images having ring structures. By way of example, it is thereby possible on board aircraft to quickly acquire gusts acting on the aircraft. The known method and the known device can be used to measure an interferogram in such a way that the position of the intensity extremes can be acquired quickly and accurately. In particular, this method may be used to determine a ring radius of an annular intensity extreme in an interferogram.
A disadvantage of the method known from DE 10 2006 030 399 B3 consists in that the position of the ring center (center) must be known in advance in order to determine the ring radii. However, the position of the ring center is generally not known, or known only insufficiently accurately (for example owing to drift of the ring center after calibration). A further disadvantage of the methodology described in DE 10 2006 030 399 B3 consists in that a slight ellipticity that may be present (for example owing to decalibrated optics) in the ring patterns of the interference image is not acquired, and therefore does not very efficiently contribute to the method (for example in a fashion so as to correct the determination of the ring radii or at the start of a new calibration). Deviations in the position of the ring center or in the shape of the ring structure from a circular shape can lead to inaccuracies with the known method. In other words, the known method operates with the desired precision only under certain circumstances.